Allow both Blish HUD and modules to promote from preview to release versions.

[dlamkins]

Both Blish HUD and modules currently treat preview releases uniquely. A preview release is determined by different factors.

Blish HUD:

• For updates: Release endpoint bool which indicates if the release is a prerelease.
• At runtime: Indicated by the version number.

Modules:

• For updates: Indicated by the packages manifest.
• Modules do not act differently at runtime.

We'd like a way to promote both module and core prereleases to standard releases. This reduces update atrophy and gives time for AV to pick up a new release without disrupting thousands of users at once.

Changes needed for Blish HUD:

• Blish HUD needs an external method of detecting release vs. prerelease.
  • We can't embed this fact with the release because the release artifact must remain the same before and after promotion to assist with AV approvals.
• Identify all runtime behaviors that are unique in prerelease builds vs. standard builds and ensure they are accounted for.
  • This is especially important for anything needed at startup as an external request to an API will delay startup.
• Update SSRD to support promoting a prerelease. We currently support prerelease deployments in SSRD, but with a minimal interface and no management options.

Changes needed for modules:

• SSRD needs the option to promote a release.
  • Both repos need updated to remove the prerelease from one and add it as a release to the other.
  • Both pkgs manifests need to be updated once done with the changes in repo (these actions will likely auto-merge).
  • We should consider allowing auto-triggering and auto-merging promotions if certain criteria is met (x number of downloads, error/fatal threshold not exceeded, etc.) as an option.